Substation u5c46

15EE2023- Substation Design Mr.P.Venkatesh Kumar

To acquire knowledge of basic substation components To understand on the constructional features and design of substations To gain basic concepts of substation automation and control

Types of substations layout and bus bar arrangements Grounding; design and Practices, substation auxiliaries, Cable routing, data acquisition, substation Control, load shedding, implementation. SCADA Communication – Substation operation substation maintenance Reference Books 1. Gupta P.V., Satnam P.S., “Substation Design and Equipment”, Dhanpat Rai Publications Private Limited, New Delhi, 2013. 2. John D. McDonald, “Electric Power Substations Engineering”, CRC Press, USA, 3 rd Edition, 2012. 3. Dominik Pieniazek P.E., “HV Substation Design: Applications and Considerations”, IEEE CED, USA, 2012. 4. Leon Kempner, “Substation Structure Design Guide”, ASCE Publications, USA, 2008. 5. Praneesh Prasad, “Substation Design”, California State University, Sacramento, 2006.

• An electrical substation is a part of an electricity generation, transmission and distribution system where voltage is transformed from high to low or in reverse using transformers. • It also serves as a point of connection between various power system elements such as transmission lines, transformers, generators and loads. • To allow for flexibility in connecting the elements, circuit breakers are used as high power switches. • Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.

• There are different kinds of substation such as Transmission substation, distribution substation, collector substation, switching substation and some other types of substation. • The general functions of a substation may include:  voltage transformation  connection point for transmission lines  switchyard for network configuration

 monitoring point for control centre protection of power lines and apparatus Communication with other substations and regional control centre

POWER TRANSFORMER : • It contains primary winding , transformer coil(inductively coupled coil)& secondary winding. • A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and in the secondary winding.

CURRENT TRANSFORMER : • When current in a circuit is too high to directly apply to measuring instruments, a current transformer is used. A current transformer has a primary winding, a magnetic core, and a secondary winding. • The alternating current flowing in the primary produces a magnetic field in the core, which then induces current flow in the secondary winding circuit POTENTIAL TRANSFORMER : • When voltage in a circuit is too high to directly apply to measuring instruments, a potential transformer is used. • Its principle of operation is same as that of power or current transformer. In this transformer the number of turns in secondary winding is less than primarywinding.

ISOLATOR : • It is essentially off load device. • Isolators are manually as well as automatically operated. • These are fitted on both sides of transformer, circuit breaker or any equipment. RELAY : • A relay is a fault sensing device on power system. • Many relays use an electromagnetism for switching mechanism. Other types of relays are –solid state relay, microprocessor based relay and Buchholz relay. CIRCUIT BREAKER : • A circuit breaker is a fault clearing device. • It is an automatically-operated electrical switch designed to protect an circuit from damage caused by overload or short circuit. • Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

BATTERY : • At 400 KV substation two sets of 220v & one set of 48 v . • The battery charging equipments comprises of a float charger and a boost charger. • Stabilization output voltage is provided in the float charger to float the battery at the correct level. The battery can be boost charging after a prolonged mains failure by the boost charger.

WAVE TRAP : • It connected is series with power line. It is basically an inductor of rating in millihenry. It blocks the high frequency carrier waves (24 kHz to 500 kHz) and let power waves (50 Hz - 60 Hz) to through.

SURGE ARRESTORS : • The protection against transient voltage surges is provided by surge arrestors. • They are usually connected between phase and ground. Surge arrestor discharges current impulse surge to earth and dissipates energy in the form of heat.

EARTH WIRE : • Earth wire in EHV transmission lines is used to provide safeguard against lightening other transient surges and efficient operation of protection system under fault condition.

• Depending on the type of equipment used, the substations could be Outdoor type with air-insulated equipment

Indoor type with air-insulated equipment Outdoor type with gas-insulated equipment

Indoor type with gas-insulated equipment Mixed technology substations

Mobile substations

•

Need Determination An active planning process is necessary to develop the business case for creating a

substation or for making major modifications. • Planners, operating and maintenance personnel, asset managers, and design engineers are among the various employees • System requirements including Load growth  System stability  System reliability  System capacity 

Customer requirements including 

Additional load

 Power quality

 Reliability  Customer relations  Customer complaints  Neighbourhood impact

Budgeting • bulk power substations need to be created or expanded in order to move large blocks of energy around the system as necessary and where do they need to be located • Determinations have to be made as to the suitability of former designs for the area in question. • To achieve this, most utilities rely on standardized designs and modular costs developed over time

• In the case of bulk power substations, the equipment and land costs can differ greatly from standard designs. • Distribution stations, however, are the most common on most systems and therefore have the best known installed costs. • Since these are the substations closest to the customers, redesign is less likely to be required than screening or landscaping, so costs do not vary greatly. • Requirements for the new station, such as voltages, capacity, number of feeders, etc., the issue of funding should then be addressed.

• This is typical when real estate investigations of available sites begin, since site size and location can significantly affect the cost of the facility. • Preliminary equipment layouts and engineering evaluations are also undertaken at this stage to develop ballpark costs, which then have to be evaluated in the corporate budgetary justification system. • Preliminary manpower forecasts of all disciplines involved in the engineering and construction of the substation should be undertaken, including identification of the nature and extent of any work that the utility may need to contract out. • This budgeting process will involve evaluation of the project in light of corporate priorities and provide a general overview of cost and other resource requirements. Note that this process may be an annual occurrence

Traditional and Innovative Design • • • • • • •

Environmental Civil Mechanical Structural Electrical—high voltage Protection and controls Communications

Substation

• functional requirements such as system and customer requirements and develops alternative design solutions. • System requirements include elements of rated voltage, rated frequency, existing system configuration (present and future), connected loads, lines, generation, voltage tolerances (over and under), thermal limits, shortcircuit levels, frequency tolerances (over and under), stability limits, critical fault clearing time, system expansion, and interconnection. • Customer requirements include environmental consideration (climatic, noise, aesthetic, spills, and right-of-way), space consideration, power quality, reliability, availability, national and international applicable standards, network security, expandability, and maintainability.

Site Selection and Acquisition

• a footprint of the station has been developed, including the layout of the major equipment • Final grades, roadways, storm water retention, and environmental issues are addressed at this stage, and required permits are identified and obtained. • Community and political acceptance must be achieved and details of station design are negotiated in order to achieve consensus.

zoning application • local government issue, • permits for grading, • storm water management, • roadway access, and other environmental or safety concerns are typically handled at the state or provincial level and • federal issues in the case of wetlands or other sensitive

areas.

the following site evaluation criteria could be used: – Economical evaluation – Technical evaluation – Community acceptance Economical evaluation

the level of affordability, return on investment, initial capital cost, and life cycle cost.

• Technical aspects Land: choose areas that minimize the need for earth movement and soil disposal. Water: avoid interference with the natural drainage network. Vegetation: choose low-productivity farming areas or uncultivated land. Protected areas: avoid any areas or spots listed as protected areas. Community planning: avoid urban areas, development land, or land held in reserve for future development.

Community involvement: engage community in the approval process. Topography: flat but not prone to flood or water stagnation. Soil: suitable for construction of roads and foundations; low soil resistivity is desirable. Access: easy access to and from the site for transportation of large equipment, operators, and maintenance teams. Line entries: establishment of line corridors (alternatives: multi-circuit pylons, UG lines). Pollution: risk of equipment failure and maintenance costs increase with pollution level.

community acceptance Adopt a low profile layout with rigid buses ed on

insulators over solid shape steel structures Locate substations in visually screened areas (hills, forest), other buildings, and trees Use gas-insulated switchgear (GIS) Use colors, lighting Use underground egresses as opposed to overhead

Design, Construction, and Commissioning Process

• Station Design • The following can be used as a guide for various design elements: 1. Basic layout a. Stage development diagram b. Bus configuration to meet single line requirements c. Location of major equipment and steel structures based on single line diagram d. General concept of station e. Electrical and safety clearances f. Ultimate stage

2. Design a. Site preparation i. Drainage and erosion, earth work, roads and access, and fencing b. Foundations i. Soils, concrete design, and pile design

c. Structures i. Materials, finishes, and corrosion control d. Buildings i. Control, metering, relaying, and annunciation buildings—types such as masonry, prefabricated, etc. ii. Metalclad switchgear buildings iii. GIS buildings e. Mechanical systems i. HVAC ii. Sound enclosure ventilation iii. Metalclad switchgear or GIS building ventilation iv. Fire detection and protection v. Oil sensing and spill prevention f. Buswork i. Rigid buses ii. Strain conductors—swing, bundle collapse iii. Ampacity iv. Connections v. Phase spacing vi. Short-circuit forces

g. Insulation i. Basic impulse level and switching impulse level h. Station insulators i. Porcelain post type insulators ii. Resistance graded insulators iii. Polymeric post insulators iv. Station insulator hardware v. Selection of station insulator—TR—ANSI and CSA standard vi. Pollution of insulators—pollution levels and selection of leakage distance i. Suspension insulators i. Characteristics ii. Porcelain suspension insulators iii. Polymeric suspension insulators iv. Suspension insulators hardware v. Selection of suspension insulators vi. Pollution of insulators—pollution levels and selection of leakage distance j. Clearances i. Electrical clearances ii. Safety clearances k. Overvoltages i. Atmospheric and switching overvoltages ii. Overvoltage protection—pipe and rod gaps, surge arresters iii. Atmospheric overvoltage protection—lightning protection (skywires, lightning rods)

Grounding i. Function of grounding system ii. Step, touch, mesh, and transferred voltages iii. Allowable limits of body current iv. Allowable limits of step and touch voltages v. Soil resistivity vi. General design guidelines Neutral systems i. Background of power system grounding ii. Three- and four-wire systems iii. HV and LV neutral systems iv. Design of neutral systems Station security i. Physical security ii. Electronic security

Station Construction – – – – – –

Parking for construction personnel traffic routing, truck activity, trailers, fencing, and mud and dirt control along with trash and noise can be major irritations for neighbors, so attention to these details is essential for achieving community acceptance.

• All the civil, electrical, and electronic systems are installed at this time. • Proper attention should also be paid to site security during the construction phase not only to safeguard the material and equipment but also to protect the public.

• Station Commissioning – it is recommended to develop an inspection, testing, and acceptance plan (ITAP).

Elements of ITAP include Factory acceptance tests (FATs) Product verification plan (PVP) Site delivery acceptance test (SDAT)

 Site acceptance tests (SATs)

Electrical Bus-Bar and its Types • An electrical bus bar is defined as a conductor or a group of conductor used for collecting electric power from the incoming feeders and distributes them to the outgoing feeders. • The bus bar system consists the isolator and the circuit breaker. • The electrical bus bar is available in rectangular, cross-sectional, round and many other shapes. • The rectangular bus bar is mostly used in the power system. • The copper and aluminium are used for the manufacturing of the electrical bus bar.

• The different types of bus bar arrangements are: 1. Single bus bar

2. Single bus bar system with sectionalization 3. Double bus bar with single breaker 4. Double bus bar with two circuit breakers 5. Breakers and a half with two main buses 6. Main and transfer bus bar

7. Double bus bar with by isolator 8. Ring bus

Double Bus Double Breaker Arrangement

Advantages of Double Bus Double Breaker •This type of arrangement provides the maximum reliability and flexibility in the supply. Because the fault and maintenance would not disturb their continuity. •The continuity of the supply remains same because the load is transferrable from one bus to another on the occurrence of the fault. Disadvantages of double bus Double breaker •In such type of arrangement two buses and two circuit breakers are used which increases the cost of the system. •Their maintenance cost is very high.

Sectionalized Double Bus Bar Arrangement.

One and a Half Breaker Arrangement

Advantages of One and a Half Breaker Arrangement It protects the arrangement against the loss of supply. The potential of the bus bar is used for operating the relay. In such type of arrangement, the additional circuits are easily added to the system. Disadvantages of One and a Half Breaker Arrangement The circuit becomes complicated because of the relaying system. Their maintenance cost is very high.

Ring Main Arrangement

Advantages of Ring Main Arrangement •Such type of arrangement will provide two paths for the supply. Thus the fault will not affect their working. •The fault is localized for the particular section. Hence the complete circuit is not affected by the fault. •In this arrangement, a circuit breaker can be maintained without interrupting the supply. Disadvantages of Ring Main Arrangement Difficulties occur in the addition of the new circuit. Overloading occurs on the system if any of the circuit breakers is opened.